Method of manufacturing flat-wire field coils

ABSTRACT

A method of manufacturing flat-wire field coils for an electric machine, especially a starter for an internal combustion engine, wherein one metallic surface only of a metal strip is coated with an adhesive lacquer and particles of rigid insulating material are disposed upon this surface and adhere to the adhesive lacquer thereof. Non-adherent particles are removed and the metal strip is coiled so that the adherent particles space apart the successive turns. The last turn is fixed to the coil which is heated and contacted with a suspension of thermoplastic or duroplastic resin powder to form a sheath around the coil. The coil is then bent to the desired shape of the field coil.

Unite States atent 1191 Prostor Apr. 10, 1973 [54] METHOD OF ACTURING 3,145,127 8 1964 Baun ..29/596 ux FLAT-WIRE FIEL IL 3,418,710 12/1968 Seidel et a1. ....29/605 X 3,440,587 4 1969 Bartos et a]. ..336/206 lnvemori Preston J h Yugoslavla 3,518,755 7 1970 Olson ....29 605 S gn e a La za v Barnum Zdruzenem podjetju Iskra, Kranj, Trzaska c. 2, Ljubljana, Yugoslavia Filed: Mar. 17, 1971 Appl. No.: 125,190

Int. Cl ..H0lf 7/06 Field of Search ..29/605; 174/ 1 1 1,

References Cited UNITED STATES PATENTS 6/1962 Abolins ..l74/1l l X Primary Examiner-Charles W. Lanham Assistant Examiner-Carl E. Hall Att0rneyKarl F. Ross [57] ABSTRACT A method of manufacturing flat-wire field coils for an electric machine, especially a starter for an internal combustion engine, wherein one metallic surface only of a metal strip is coated with an adhesive lacquer and particles of rigid insulating material are disposed upon this surface and adhere to the adhesive lacquer thereof. Non-adherent particles are removed and the metal strip is coiled so that the adherent particles space apart the successive turns. The last turn is fixed to the coil which is heated and contacted with a suspension of thermoplastic or duroplastic resin powder to form a sheath around the coil. The coil is then bent to the desired shape of the field coil.

8 Claim, 6 Drawing Figures PATENTEI] APR 1 [H973 FIG. 4

METHOD OF MANUFACTURING FLAT-WIRE FIELD COlLS l. FIELD OF TI-IE INVENTION The present invention relates to a method of manufacturing fiat-wire field coils intended to be mounted into electric machines, particularly into starters of intemal-combustion engines.

2. BACKGROUND OF THE INVENTION 3. SUMMARY OF THE INVENTION The aim of the invention is to avoid these disadvantages and replace the paper insulation by another insulating material, whereby other stages of coil manufacture are also improved. According to the invention this object is achieved in the manner that on its broadside the flat wire is covered by an insulating material preferably of mineral origin, such as quartz (silica), corundum or the like, with particles of a definite thickness of 100, 150 or 200 pm, and these particles are fixed to the flat wire because of a previously applied adhesive. By the thickness of the particles, the layer of the insulating particles adhering defines the distance between the turns. Due to this insulation the coil is temperature-resistant, which makes it possible to anneal it by joulean heat after coiling in order to remove the internal stresses arising in the copper wire during coiling. Advantageous is electric annealing of a half of the last external turn. Thereby the coil will maintain its shape and the prior systems of fixing the last turn becomes superfluous.

4. DESCRIPTION OF THE INVENTION The method of manufacturing the coil according to the invention will be described in detail with reference to the accompanying drawing, in which:

FIG. 1 shows the application of insulating particles to the fiat wire;

FIG. 2 shows the coil after accomplished coiling, with the fixed last turn;

FIG. 3 shows the coil with the electrodes applied for joulean heating of a half of the last external turn, in order to reduce internal stresses;

FIG. 4 shows the coil after application of the solidifying and insulating sheath;

FIG. 5 is a sectional elevation of the coil before the final fashioning, and

FIG. 6 is a sectional elevation of the coil after the final fashioning.

5. SPECIFIC DESCRIPTION The fiat wire 10 according to FIG. 1, which is still bare in its right part 11, is coated before coiling with a lacquer 12 which adheres well to the wire. Upon the fresh lacquer coating 12 which only serves as adhesive,

spacing particles 13 of an insulating mineral material, such as quartz (silica), corundum, ceramics, of a definite size of 100, 150 or 200 um are scattered as this is shown in the right part of FIG. 1. The particles first impinged adhere to the wire surface while the rest can be removed, e.g., by blowing. In the case of series production, this spacing insulating layer is applied only to the wire parts of definite and necessary length so that the ends of the coil do not show any insulation.

Coiling of the coils proceeds according to known methods; for the securing of the last turn there exist two possibilities. First, the last turn can be held by a cord 14 (FIG. 2) having such a heat resistance that it 5 withstands the heating of the coil during its insulation.

On the other hand, it is possible to anneal the coil 18, its external turn 17 or only a part of the external turn by applying two electrodes 15, 16 (FIG. 3), whereby the turns of the coil remain in the required position due to the removal of internal stresses.

By the heat resistance of a coil manufactured by the method according to the invention, the use of powdery insulating materials 19 requiring also high preheating temperatures, such as epoxy resins (up to 230C), polyamides (up to 240400C), pentones (up to 260350C), and teflons (up to 430540C), is rendered possible for solidifying and sheathing the coil.

Sheathing of the coil proceeds according to known methods by thermoplastics, preferably polyamides, or by duroplastics, preferably powdery epoxy resins, in a bath with suspended powdery particles or by sprinkling in an electrostatic field or without a field as well as with simultaneous or subsequent sintering and in a given case with additional heat treatment. The sheath 20 comprises the coil 21 itself and the leadins 22 without the terminations which must remain non-insulated (FIG. 4).

The coil is advantageously preheated by joulean heat which renders possible maintenance of the temperature required also during the application of the insulating material of the sheath. For the insulating sheath, advantageously, thermoplastic powders are used, whereby a coil with such a sheathing has only to be cooled down after accomplished sintering. With a proper treatment, the insulating material 20 penetrates deeply between the turns 23 so that the spacing layer 19 is partially impregnated (FIG. 5), whereby a subsequent bending of the coil to the shape required is possible without damage (FIG. 6).

What we claim is:

l. A method of making a flat-wire field coil for an electric machine, comprises the steps of:

a. continuously coating a single metallic surface of a metal strip with an adhesive lacquer prior to coiling of said strip;

b. continuously dispersing on the lacquer-coated metallic surface rigid insulating particles of a defined particle size ranging between and 200 microns to cause at least some of said particles to adhere to said surface in the form of a layer of adherent particles;

c. thereafter removing nonadherent particles from said surface;

d. winding said metal strip into a coil with said layer of adherent particles interposed between the successive turns;

e. fixing the last of said turns to the remainder of said coil;

f. electrically preheating said coil to a temperature sufficient to cause synthetic resin powder selected from the group which consists of thermoplastic and duroplastic powders to bond to said coil, and contacting said coil with said powder to form a sheath of the resin around said coil; and

g. bending the sheathed coil to a final configuration.

2. The method defined in claim 1 wherein said particles are composed of a thermoplastic and said coil remains unheated following the bonding of the thermoplastic particles to the coil.

3. The method defined in claim 1 wherein said coil is coated with a duroplastic and is heated subsequent to application of the particles of duroplastic to the coil.

4. The method defined in claim 1 wherein said last turn is secured to the remainder of the coil by binding it with a cord.

5. The method defined in claim 1 wherein said last turn is secured to the remainder of said coil by contacting said last turn with a pair of spaced apart electrodes and passing an electric current through said strip to heat said last turn.

6. The method defined in claim 1, further comprising the step of maintaining termini of said strip free from said lacquer and the insulating particles applied in step(b)whereby said termini lie outwardly of said sheath.

7. The method defined in claim 1 wherein the particles applied to said coil are composed of thermoplastic selected from the group which consists of teflon, polyamides and pentones.

8. The method defined in claim 1 wherein the powder applied to said coil is an epoxy resin. 

2. The method defined in claim 1 wherein said particles are composed of a thermoplastic and said coil remains unheated following the bonding of the thermoplastic particles to the coil.
 3. The method defined in claim 1 wherein said coil is coated with a duroplastic and is heated subsequent to application of the particles of duroplastic to the coil.
 4. The method defined in claim 1 wherein said last turn is secured to the remainder of the coil by binding it with a cord.
 5. The method defined in claim 1 wherein said last turn is secured to the remainder of said coil by contacting said last turn with a pair of spaced apart electrodes and passing an electric current through said strip to heat said last turn.
 6. The method defined in claim 1, further comprising the step of maintaining termini of said strip free from said lacquer and the insulating particles applied in step(b)whereby said termini lie outwardly of said sheath.
 7. The method defined in claim 1 wherein the particles applied to said coil are composed of thermoplastic selected from the group which consists of teflon, polyamides and pentones.
 8. The method defined in claim 1 wherein the powder applied to said coil is an epoxy resin. 